The present invention relates to a flat display apparatus with spacers between a first panel substrate and a second panel substrate and a method of manufacturing the same.
When an electric field above a threshold value is applied to the surface of a conductor, such as a metal, or a semiconductor placed in vacuum, electrons pass through a potential barrier under the tunnel effect, and the electrons are emitted into the vacuum even at normal temperature. This phenomenon is called field emission, and a device emitting electrons by field emission is called a field emission device.
In recent years, attention has been paid to a field emission display (FED) in which a field emission device of the Spindit type, the thin film type, or the like are used as an emitter. The FED is a flat display apparatus in which a multiplicity of field emission devices are provided on a cathode electrode by use of semiconductor technology or the like. The FED is a system in which electrons are emitted by field concentration from the field emission devices in an electron emission unit, which are selected electrically, the electrons are caused to impinge on phosphors on the anode substrate side, and excitation or light emission of the phosphors is induced, whereby an image is displayed.
The FED has a structure in which a cathode substrate and an anode substrate are disposed opposite to each other, with a minute gap therebetween, and the gap space portion in a vacuum condition is encapsulated. Therefore, in order that the cathode substrate and the anode substrate can endure the atmospheric pressure, spacers are mounted between the substrates so as to support the substrates by the spacers.
The FEDs are generally classified into the low voltage type and the high voltage type, according to the level of the voltage impressed on the anode electrode for causing an electron beam to impinge on the phosphors to induce light emission, namely, the anode voltage. The spacers, particularly those used in a high voltage type FED, have a very high aspect ratio; for example, the spacers have a height of 1 to 2 mm and a thickness of 0.05 to 0.1 mm. Therefore, it is difficult for the spacers to stand on the substrate by themselves. Accordingly, some means for supporting the spacers is needed.
However, in the process of manufacturing an FED, it is necessary to mount a large number of spacers on the substrate, according to the screen size. Therefore, in the case of an FED with a large screen size, it is demanded to simplify the process of mounting the spacers. For the conventional FEDs, there have been used a method of fixing the spacers on the substrate by use of an adhesive, a method of supporting the spacers by sandwiching them between pairs of glippers provided on the substrate correspondingly to the thickness of the spacers, and so on. Such methods, however, have the drawback that a series of manufacturing steps, such as chucking of the spacers and positioning of the spacers, are very complicated. In addition, in the method of using the pairs of glippers, it is necessary to insert each spacer into the gap between the pair of glippers so as to clamp the spacer. In order to obtain an appropriate clamping force, it is necessary to rigorously control the gap size of the pairs of glippers and the thickness of the spacers, and such control requires much labor and cost.